I' m Thomas.
my question is:
How to change in a simple way the design of Zen amplifier
in order to be suitable for such loudspeakers:
8 ohm, 88 dB, 100 W (rated power) ?
or maybe someone can suggest another project based on
very simple topology.
Thank you in advance.
Best regards
Tomasz Rodak

To get more power, you'll need to consider paralleling two Zen amps or simply making the original design larger; use higher rails, set higher bias currents, and use bigger MOSFETs. (This is not at all difficult to do, just proceed slowly and all will be well.)
Or you can see what Nelson releases on the www.passdiy.com site.